1. Field of the Invention
The present invention relates to a method of producing an ink jet recording head, an ink jet recording head produced by the method and an ink jet recording apparatus. In particular, the present invention relates to a method of producing an ink jet recording head whose discharge port is formed by use of laser beam, an ink jet recording head produced by the method, and an ink jet recording apparatus.
2. Related Background Art
To work a discharge port (orifice) of an ink jet recording head an excimer laser beam has been recently often used. As disclosed in Japanese Patent Application Laid-Open No. 2-121843 and No. 2-187346 which corresponds to U.S. Pat. No. 5,208,604, working of an orifice by the use of excimer laser beam has been typically carried out by irradiating a discharge port forming member (orifice plate) of a top plate which integrally has a groove member in which a groove of a flow path of recording liquid (ink) was formed and a discharge port member which is positioned at the front of this groove and has a comparatively thin thickness, with excimer laser beam. Further, these Applications also disclose a method of working a taper-shaped orifice whose sectional area is gradually reduced in the discharge direction by irradiation of excimer laser from the groove side of the flow path of the top plate.
The summary of the prior art method will now be described with reference to FIGS. 6 and 7. FIG. 6 is a schematic perspective view showing a conventional ink jet recording head. FIG. 7 is a schematic cross-sectional view of FIG. 6.
In the ink jet recording head shown in FIG. 6, a substrate 602 and a top plate 608 are formed while they are connected to each other. The substrate 602 is provided with an energy generator which generates energy which is utilized for discharging ink. The ink jet recording head shown in FIG. 6 is provided with electrothermal converting elements 601 which generate thermal energy as energy generators respectively. The grooves 603 which form ink paths are formed in the top plate 608 so that they correspond to the electrothermal converting elements 601, respectively. A discharge port forming member 605 is integrally provided on the top plate 608 at the end portion of the groove 603 so that an ink discharge port 604 is communicated with the groove 603. To the ink flow path is supplied ink from a common ink chamber 606 defined with a frame 607.
A top plate is provided with a groove 701, a discharge port 702, a discharge port forming member 703, a common ink chamber 704, a frame for the ink chamber and the like. The reference numeral 707 denotes excimer laser beam irradiated for working the discharge port 702 through desired optical systems. The reference numeral 708 denotes a laser beam axis of the excimer laser beam 707. The reference numeral 709 denotes the central axis of the groove 701. Further, the reference numeral 710 denotes a straight line l obtained by connecting the center p of gravity on plane P rectangular to the central axis 709 of the groove to the center q of gravity of the discharge port on a plane Q other than the plane P rectangular to the central axis 709 of the groove.
In such working of the discharge port by use of excimer laser beam, shown in FIG. 7, the straight line l 710 is not made to be parallel to the central axis 709 of the groove so that the discharge port 702 has a tapered-shape whose sectional area is reduced in the discharge direction. Further, the laser beam axis 708 becomes the same as the straight line l 710. As the result, ink is discharged in the extended direction of the laser beam axis 708. In this connection, a recording medium surface is shown in FIG. 7, for reference.
The discharge port shown in Japanese Patent Application Laid-Open No. 2-187346 has a structure which can stably obtain the amount and discharge rate of ink droplets. However, to obtain higher-definition images in the ink jet recording head, there still remains the following problems.
Namely, the discharge port 702 has the above-mentioned structure or shape, ink droplets cannot reach the recording medium surface in the vertical direction thereto. This depends on the method of working the discharge port by the use of excimer laser shown in FIG. 7. This reason is that when the excimer laser beam 707 is radiated from a groove side of the ink flow path in the ink chamber, the excimer laser beam must be radiated at a certain angle (xcex81) so that no excimer laser beam 707 reaches the frame 705 of the ink chamber. The above-mentioned Japanese Patent Application Laid-Open No. 2-187346 discloses xcex81=10xc2x0. It is physically impossible to have condition xcex81=0xc2x0 without the irradiation of the frame 705 of the ink chamber with excimer laser beam 707. On the other hand, when the frame 705 of the ink chamber is irradiated with excimer laser beam 707, no discharge port can be worked. A method of providing the frame 705 of an ink chamber later is considered so that the condition xcex81=0xc2x0 can be obtained. However, it is actually impossible to strongly and positively adhere the frame 705 of the ink chamber, which is a minute portion, without imparting change to ink and with adhesive having resistance to ink.
Thus, there are no ways other than discharging ink droplets at the angle xcex81 of the laser beam axis from the discharge port using the working method described in Japanese Patent Application Laid-Open No. 2-187346. As mentioned above, since the xcex81 always has an angle larger than 0xc2x0, there are no ways other than tilting a top plate or recording medium to cause the ink droplets to reach the recording medium surface in the vertical direction thereto. Further, any method thereof has complicated and large-scale configuration, it is not always an appropriate means.
Next, the reason why obtaining high-definition images is impossible when ink droplets cannot vertically arrive at the recording medium surface, will be described. FIG. 8 is a schematic view showing the state of arrival of the ink droplets at the recording medium surface (paper surface). In FIG. 8 the reference numeral 801 denotes an ink droplet A discharged at a certain angle xcex81 and the numeral 802 denotes an ink droplet B discharged without having a certain angle xcex81. The reference numeral 803 denotes an ideal recording medium A, and the numeral 804 denotes an actual recording medium B. The reference numeral 805 denotes the arrival position A where the ink droplet A 801 discharged at a certain angle xcex81 arrives at the ideal recording medium A 803, 806 denotes the arrival position B where the ink droplet A 801 discharged at a certain angle xcex81 arrives at the actual recording medium B 804, 807 denotes the arrival position C where the ink droplet B 802 discharged without having a certain angle xcex81 arrives at the ideal recording medium A 803, and 808 denotes the arrival position D where the ink droplet B 802 discharged without having a certain angle xcex81 arrives at the actual recording medium B 804.
The actual recording medium B 804 has a flexible shape, which is different from the ideal recording medium A 803. When an ink droplet like the ink droplet A 801 arrives at the recording medium at a certain angle, difference occurs between the arrival position A 805 of the ink droplet and the arrival position B 806 thereof by the flexibility of the recording medium B 804 (in X direction in FIG. 8). However, when an ink droplet like the ink droplet 802 arrives at the recording medium without having a certain angle, even though the recording medium B 804 has flexible curved surfaces, there is no difference between the ink droplet arrival position C 807 and the ink droplet arrival position D 808. The above-mentioned points are important to attain a higher definition printing in the ink jet recording.
One object of the present invention is to provide a method of producing an ink jet recording head which can attain a high-definition image recording easily and at a low cost, an ink jet recording head produced by the production method, and an ink jet recording apparatus.
Another object of the present invention is to provide a method of producing an ink jet recording head comprising the steps of:
forming a discharge port by irradiating a discharge port forming member, which is integrally provided on a top plate provided with a groove of an ink flow path communicated with said discharge port for discharging ink, and in which said discharge port is formed, with a laser beam having ununiform intensity distribution of the light beam, from said groove side; and
forming said ink flow path by connecting said top plate to a substrate, with said groove being positioned inside.
Still another object of the present invention is to provide an ink jet recording head, in which an ink flow path is formed by connecting a top plate integrally having a discharge port forming member in which a discharge port for discharging ink is formed, and which is provided with a groove of said ink flow path communicated with said discharge port, to a substrate, with said groove positioned inside;
wherein said discharge port is formed by irradiating said discharge port forming member with a laser beam having ununiform intensity distribution of the light beam, from said groove side, and wherein if the centers of gravity of the configuration obtained by cutting said discharge port forming member by two planes P and Q rectangular to the central axis of said groove are defined as p and q, respectively, the straight line l formed by connecting the center p of gravity to the center q of gravity is substantially parallel to the central axis of said groove.
Still another object of the present invention is to provide an ink jet recording apparatus including such ink jet recording head and a member on which said ink jet recording head is placed.
According to the present invention, the direction of ink which flows in the flow path can be caused to coincide with the direction of ink which flows in the discharge port, whereby the flow of ink can be stabilized and ink can be efficiently and stably discharged.
In an ink jet recording head of the present invention, preferably, the straight line formed by connecting the center p of gravity to the center q of gravity is substantially vertically intersected to the outer surface of the discharge port forming member. Accordingly, an ink jet recording head of the present invention can prevent the effects of change of minute wettability having the discharge forming member, and can further stably discharge ink.
Further, in a method of producing an ink jet recording head of the present invention, a discharge port configuration which can discharge ink without depending on the laser beam axis can be produced with a laser beam through a mask, easily and at a low cost. According to the present invention, ink can be discharged without relation to the axis of laser beam by which a discharge port can be worked. As the result, ink can be discharged in a desired direction without tilting the recording medium or ink jet recording head.
Further, according to the present invention, ink can arrive at the recording medium in vertical direction thereto. Therefore, an ink jet recording head which is not influenced by cockling in the transportation of the recording medium can be produced and a high-definition image can be recorded. At the same time, the axis of the groove can be in substantially parallel to the axis of the orifice and ink can be stably discharged. Further, according to the present invention, working of the ink jet recording head is easy and the working accuracy is stabilized. As the result, an ink jet recording head which can record a high-definition image can be provided at a low cost and on a mass production.